Fabrication of semi-polar crystal structures

Abstract

A method of growing a group III nitride crystal structure comprises: providing a silicon substrate ( 12 ); forming a first mask ( 10 ) on the substrate, the mask having a plurality of apertures ( 14 ) through it each exposing a respective area of the silicon substrate; etching the silicon exposed by each of the apertures to form a respective recess ( 16 ) having a plurality of facets ( 18, 20, 22, 24 ); depositing a second mask over some of the facets of each recess leaving at least one of the facets ( 22 ) of each recess exposed; and growing group III nitride on the exposed facets ( 22 ) and then over the substrate to form a continuous layer.

The invention claimed is: 
     
       1. A method of growing a group Ill nitride crystal structure comprising the steps of:
 providing a silicon substrate; 
 forming a first mask on the substrate with a plurality of apertures formed through the mask arranged in a 2D array, each of the apertures exposing a respective area of the silicon substrate; 
 etching the silicon exposed by each of the apertures to form a respective recess having a plurality of facets; 
 depositing a second mask over areas between the recesses and over some of the facets of each of the recesses leaving only one of the facets of each of the recesses exposed; and 
 growing group III nitride on the exposed facets and then over the substrate to form a continuous layer covering the recesses. 
 
     
     
       2. The method according to  claim 1  wherein the etching is performed using anisotropic wet etching. 
     
     
       3. The method according to  claim 1  wherein each of the facets of each of the recesses is substantially triangular or trapezoidal. 
     
     
       4. The method according to  claim 1  wherein each of the recesses has a bottom and tapers to a point at the bottom. 
     
     
       5. The method according to  claim 1  wherein one of the facets of each of the recesses is a (1-11) facet which is left exposed for growth of the group III nitride thereon. 
     
     
       6. The method according to  claim 5  wherein the group Ill nitride grows initially as (0001) group III nitride on the (1-11) silicon facet of each of the recesses, and the group III nitride then grows out of the recesses and merges to form a single layer of (11-22) group III nitride. 
     
     
       7. The method according to  claim 1  wherein a buffer layer is deposited on the exposed facets prior to the growth of the group III nitride. 
     
     
       8. The method according to  claim 1  wherein the apertures are arranged in a regular 2D array. 
     
     
       9. The method according to  claim 1  wherein the group III nitride is at least one of GaN, AlGaN, InGaN, and AlN.